subnetting - RFC1878 - 000's & 111's

I was putting together some subnetting tables,
and posted a couple of other msgs about subnetting.

One of the questions that came up,
was how to handle the 000 and 111 subnets ?
(the first and last subnets)

I've found that RFC1878 says everything is ok now,
but that RFC was written in December 1995.

So - if we have some old cisco 2501's running,
from 1997 with - version 11.3 -
or even some other routers that were acquired, installed,
and have been just plain running for years -
How should we view the RFC1878 issue ?

What about other networks out there ?
How many are using the 000 and 111 subnets ?

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"Phil Schuman" <> writes:
>I was putting together some subnetting tables,
>and posted a couple of other msgs about subnetting.
>One of the questions that came up,
>was how to handle the 000 and 111 subnets ?
> (the first and last subnets)

No problems in using them generally now. There were only a few odd
problems with a few things out there that have been all fixed now.
I think Novell was the worst offender, earlier versions of Netware IP
(ie. stuff that would work back on Netware 3.xx??) failed to work correctly.
Maybe Novell Bordermanager as well. Some HP stuff.

Most normal stuff never had any problem with all 0's and all 1's subnets.
>I've found that RFC1878 says everything is ok now,
>but that RFC was written in December 1995.

Yep. Haven't had to deal with any customer having any issues since the
late '90s at least.
>So - if we have some old cisco 2501's running,
>from 1997 with - version 11.3 -
>or even some other routers that were acquired, installed,
>and have been just plain running for years -
>How should we view the RFC1878 issue ?

Pretty much non issue. Just 'ip subnet-zero' on all routers, and away
you go. Cisco has supported that for quite some time, long before 1997.
>How many are using the 000 and 111 subnets ?

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